b&b in le Marais, Paris.

Michele,
This is not a B&B so you may not be interested. On my last stay in the Marais I walked right by the MIJE youth hostel and it was in a fantastic location (between the St Paul and Pont Marie metros). I have no idea about its quality or if it offers private rooms. Just thought I would mention in case this was something you would consider.

MIJE has three hostels in the Marais. They are renovated 17th-century private mansions. Rick Steves calls them "the best budget accommodations in Paris." A simple continental breakfast is included and private rooms are available. See here.

Paris is a large urban area and not really a "B&B" kind of place: like looking for a B&B in Manhattan. But there are hotels that serve breakfast, if that's what you meant. And several of those have already been suggested.

Are you staying for as long as a week? There are a myriad of apartment rental agencies, most of them cheaper than a hotel. Vacationinparis.com, VRBO.com, airbnb.com, rentparis.com, parisvacationapartments.com. The list goes on.

You might want to consider Maison Zen, which is near Place de la Bastille - http://www.maisonzen.com/

If you are considering a relatively inexpensive hotel, I stayed at Hotel Jeanne d'Arc this past October (3, rue de Jarente). Fantastic price for a fantastic location, wonderful and friendly staff, and a delicious breakfast for 6 euros. However, the walls are super thin, so you can hear your neighbors snoring or coughing or talking, etc. If your room faces onto Rue de Jarente, be prepared for lots of street noise at night and 8 a.m. very loud garbage trucks. They have a computer in a back room for guests (not a QUERTY keyboard).

There may be exceptions, but most Paris hotels are not "B&B" but charge extra for breakfast. For B&B you might look into staying at a hostel. The MIJE hostels are in the RS book (Paris) and come highly recommended. There are three of these hostels in the Marais.

Thanks everyone for the replies!
Well, we are staying only 2 nights.
For b&b I actually ment a family run, unexpensive place to stay.
Or any other accomodation, as long as it is clean :-) i will look at the ones you suggested.
Thanks!